Tap for coaxial cable transmission lines



April 12, 1955 D. DUDRA 2,706,282

TAP FOR COAXIAL CABLE TRANSMISSION LINES Filed March 22, 1954 Tlzrl 4i.2

/N VE N TOR DAN/E L 'DUDRA mazzzwg A TTORN'FV Unitcd States Patent TAPFOR COAXIAL CABLE TRANSMISSION LINES Daniel Dudra, Kulpmont, Pa.Application March 22, 1954, Serial No. 417,739 Claims. (Cl. 339-97) Thisinvention relates to the art of taps for electrical conductors, and,more particularly, to a novel and improved tap which is particularlyadapted for use on coaxial cable transmission lines.

While there have been numerous attempts in the past to providesatisfactory taps for electrical conductors of one sort or another, sofar as I am aware, there have been but few developments along the linesof a tap which may be efiiciently used on coaxial cable transmissionlines.

Accordingly, it is among the objectives of the present invention toprovide an electrical tap which may be used on coaxial cabletransmission lines with high efficiency.

Another object is the provision of a device of the class described whichmay be quickly and easily attached, yet durable in service.

Another object is to provide a device which, while possessed of theforegoing advantages, may be easily and inexpensively manufactured.

The invention, then, comprises the features hereinafter fully describedand as particularly pointed out in the claims, the following descriptionsetting forth in detail certain illustrative embodiments of theinventiori, these being indicative of but one of a number of ways inwhich the principles of the invention may be employed.

In said drawings:

Figure 1 is a longitudinal sectional view of a device which has beenmade in accordance with the teachings of the present invention, the samebeing shown as applied to a standard form of coaxial transmission cable;

Figure 2 is an end view taken from the left-hand end of Figure 1;

Figure 3 is an exploded longitudinal view of the elements of the deviceof Figure l; and

Figure 4 is a view which is generally similar to Figure 3, but showingthe various elements thereof in end elevation.

Referring more particularly to the drawings, the letter A designates thecenter conductor of a conventional coaxial cable transmission line, thesame also comprising a relative thick surrounding layer B of plasticinsulation, such as of the Teflon or Styrene variety. This plasticinsulation B is covered by a metallic electrically conductive groundbraid C which is, in turn, covered by an outside layer D of standardinsulating material, such as rubber.

At the left-hand end of Figure 1, there is illustrated a coaxial cabletransmission tap-01f line which is composed of elements a, b, c, and dwhich correspond to the aforementioned elements A, B, C, and D,respectively, of the larger coaxial cable, but are considerably smallerin SlZC.

According to the teachings of the present invention, there is provided agenerally tubular main body member 2, one end of which is externallyscrew-threaded, as at 4. This externally screw-threaded main body member2 is provided with a slot 6, the side walls of which are straight, andthe distance between them sutiicient to accommodate the larger coaxialtransmission cable. The bottom of this slot 6 is curved, as at 8, insuch manner as to form a seat for the larger coaxial cable.

The opposite end of the generally tubular main body member 2 is providedwith a bore 10 which is screwthreaded, as at 12; and this bore 10communicates through a smaller cylindrical bore 14 with a cylindricalchamber 16.

The outer end of the cylindrical chamber 16 opens onto the curved bottom8 of the cable-receiving slot 6, while its inner end connects with thebore 10 through a bevelled portion 18. i

The cylindrical chamber 16 is adapted to receive a cartridge 20 ofsimilar size and shape which is composed of plastic insulating material(which, again, may be of the Teflon or Styrene variety). Disposed withinthe cartridge 20 is a small cylindrical resistor 22 which is providedwith an elongate slot 6 for a distance which is approximately the sameas the radius of the large coaxial cable. This elongate projecting pin24 carries a sleeve 25 of suitable plastic insulating material, such asTeflon.

The outer end 26 of the projecting pin 24 is of arrow shape and therearward portion thereof forms a shoulder 28 against which the outer endof the sleeve 25 seats.

The other end of the resistor 22 is provided with a minute centrallydisposed recess (not shown) for receiving the end of the centralconductor wire a of the smaller coaxial cable which is illustrated atthe left of Figure 1. This minute centrally disposed recess in the innerend of the resistor 22 communicates with the small cylindrical bore 10(in the main body member 2) through a small opening 30 in the center ofthe rearward end wall of the cartridge 20.

An exteriorly threaded ferrule 32 is received in the bore 10 inscrew-threaded engagement with the threads 12 thereof; and the outer endof this ferrule (32) is provided with a wrench-receiving head 34 whichis adapted to seat against the adjacent end of the main body member 2.

A block 36 is disposed in the slot 6 in the main body member 2; and itsinner end is concaved, as at 38, in the manner of the cable-contactingbottom 8 of said s ot.

This concaved inner end 38 of the block 36 is provided with a pair ofpointed pins 40 which project sufiiciently to enable them to penetratethe outer insulation D of the large coaxial cable and make electricalcontact with the metallic electrically-conductive ground braid C.

The block 36 is forced against the large coaxial cable by means of a cap42 which screw-threadedly engages the threaded portion 4 of the mainbody portion 2.

As previously mentioned, the block 36 (which carries the pins 40) isforced against the large coaxial cable by means of the screw-threadedengagement of the cap 42 with the main body portion 2 of the tap of thepresent invention. It will, of course, be understood that this movementof the block 36 toward the large coaxial cable will be accompanied bythe movement of the large coaxial cable onto, and over, the elongateprojecting pin 24 which is carried by the cartridge 20.

With the cartridge 20 and its interiory disposed resistor seated in thecylindrical chamber 16, the outer insulation d of the smaller coaxialcable is peeled back a distance but slightly greater than the length ofthe small cy.indrical bore 14; and the metallic electrically-conductiveground braid c is laid bare for a small distance (say, of an inch). Thisground braid c of the smaller coaxial cable is pushed back from theinsulation b and over it a washer 44 is placed. These parts are thenfitted in to the bore 10 which permits the projecting end of the centralconductor wire a to extend through the small central opening in therearward end wall of the cartridge 20 and to seat in the minutecentrally disposed recess (not shown) in the back of the resistor 22.

The ferrule 32 is then inserted and its inner end forces the washer 44to firmly hold the ground braid c against the bottom of the bore 10 ofthe main body member 2.

In the foregoing manner, there is provided an excellent connection forthe ground braid c of the smaller coaxial cable through the main bodymember 2 and its block 36 and pointed pins 40 to the ground braid C ofthe larger coaxial cable.

The arrow-shaped end 26 of the projecting pin 24 of the resistor 22enters the central conductor wire A of the large coaxial cable to makefirm electrical contact therewith.

The plastic insulating B, under pressure, flows around the projectingpin 24 from the shoulder 28 of the arrowshaped end 26 rearwardly to itspoint of connection with the resistor 22. In this manner, the projectingpin 24 is effectively insulated from the ground braid C.

According to the foregoing construction and arrangement, there isprovided a device which attains all of the objectives set forthhereinbefore; and one which is also waterproof.

While I have shown and described certain specific embodiments of thepresent invention, it will be readily understood by those skilled in theart that I do not wish to be limited exactly thereto, since variousmodifications may be made without departing from the scope of theinvention as defined in the appended claims.

I claim:

1. A tap for transferring electrical energy from along the length of acoaxial transmission cable of the type comprising a central conductorand a radially disposed concentric ground conductor; said tap comprisinga generally tubular electrically conductive member having a transverserecess which receives a peripheral portion of said cable, a pin disposedin said recess and in insulated relationship with respect to saidfirst-named member, said pin penetrating said cable to the extent ofmaking electrical contact with its central conductor but not itsconcentrically disposed ground conductor, a second memberscrew-threadedly engaging said first-named member, a pin carried by saidsecond-named member and penetrating said cable to the extent of makingelectrical contact only with its aforementioned ground conductor, saidpin being in electrical contact with said first-named member, a thirdmember, said third member being in screw-threaded engagement with saidfirst-named member, and a coaxial cable transmission tap-off cablecomprising a central conductor and a radially disposed concentric groundconductor, said coaxial transmission tap-off cable having one of itsends disposed in said third-named member, the central conductor of saidcoaxial transmission tap off cable being in electrical contact with saidfirst-named pin, the ground conductor of said coaxial transmissiontapolf cable being in electrical contact with said first-named member.

2. A tap for transferring electrical energy from along the length of acoaxial transmission cable of the type comprising a central conductorand a radially disposed concentric ground conductor; said tap comprisinga generally tubular electrically conductive member having a transverserecess which receives a peripheral portion of said cable, a pin disposedin said recess and in insulated relationship with respect to saidfirst-named member, said pin penetrating said cable to the extent ofmaking electrical contact with its central conductor but not itsconcentrically disposed ground conductor, a second electricallyconductive member screw-threadedly engaging said first-named member, apin carried by said secondnamed member and penetrating said cable to theextent of making electrical contact only with its aforementioned groundconductor, a third member, said third member being in screw-threadedengagement with said first-named member, and a coaxial transmissiontap-off cable comprising a central conductor and a radially disposedconcentric ground conductor, said coaxial transmission tapolf cablehaving one of its ends disposed in said thirdnamed member, the centralconductor of said coaxial transmission tap-off cable being in electricalcontact with said first-named pin, the ground conductor of said coaxialtransmission tap-oif cable being in electrical contact with saidfirst-named member.

3. A tap for transferring electrical energy from along the length of acoaxial transmission cable of the type comprising a central conductorand a radially disposed concentric ground conductor; said tap comprisinga generally tubular electrically conductive member having a transverserecess which receives a peripheral portion of said cable, a pin disposedin said recess and in insulated relationship with respect to saidfirst-named member, said pin penetrating said cable to the extent ofmaking electrical contact with its central conductor but not itsconcentrically disposed ground conductor, a second electricallyconductive member screw-threadedly engaging said first-named member, apin carried by said secondnamed member a'ndpenetrating said cable to theextent of making electrical contact only with its aforementioned groundconductor, a third electrically conductive member, said thirdelectrically conductive member being in screw-threaded engagement withsaid first-named member, and a coaxial transmission tap-off cablecomprising a central conductor and a radially disposed concentric groundconductor, said cdaxial transmission tap-off cable having one of itsends disposed in said third-named member, the central conductor of saidcoaxial transmission tap-off cable being in electrical contact with saidfirstnarned pin, the ground conductor of said coaxial transmissiontap-off cable being in electrical contact with said first-named memberand said third-named member.

4. A tap for transferring electrical energy from along the length of acoaxial transmission cable of the type comprising a central conductorand a radially disposed concentric ground conductor; said tap comprisinga generally tubular electrically conductive member having a transverserecess which receives a peripheral portion of said cable, a pin disposedin said recess and in insulated relationship with respect to saidfirst-named member, said pin penetrating said cable to the extent ofmaking electrical contact with its central conductor but not itsconcentrically disposed ground conductor, a second electricallyconductive member screW-threadedly engaging said first-named member, apin carried by said secondnamed member and penetrating said cable to theextent of making electrical contact only with its aforementioned groundconductor, a third electrically conductive member, said thirdelectrically conductive member being in screw-threaded engagement withsaid first-named member, and a coaxial transmission tap-off cablecomprising a central conductor and a radially disposed concentric groundconductor, said coaxial transmission tap-off cable having one of itsends disposed in said third-named member, the central conductor of saidcoaxial transmission tap-off cable being in electrical contact with saidfirstnamed pin, a portion of the ground conductor of said coaxialtransmission tap-off cable being clamped between said first-named memberand said third-named member.

5. A tap for transferring electrical energy from along the length of acoaxial transmission cable of the type comprising a central conductorand a radially disposed concentric ground conductor; said tap comprisinga generally tubular electrically conductive member having a transverserecess which receives a peripheral portion of said cable, a pin disposedin said recess and in insulated relationship with respect to saidfirst-named member, said pin penetrating said cable to the extent ofmaking electrical contact with its central conductor but not itsconcentrically disposed ground conductor, an electrically conductiveblock disposed in said recess, a second electrically conductivememberscrew-threadedly engaging said firstnamed member and serving toforce said block against said cable, a pin carried by said block andpenetrating said cable to the extent of making electrical contact onlywith its aforementioned ground conductor, a third electricallyconductive member, said third electrically conductive member being inscrew-threaded engagement with said first-named member, and a coaxialtransmission tapoff cable comprising a central conductor and a radiallydisposed concentric ground conductor, said coaxial trans! missiontap-off cable having one of its ends disposed in said third-namedmember, the central conductor of said coaxial transmission tap-off cablebeing in electrical contact with said first-named pin, a portion of theground conductor of said coaxial transmission tap-off cable beingclamped between said first-named member and said thirdnamed member.

References Cited in the file of this patent UNITED STATES PATENTS2,196,964 Let: Apr. 9, 1940 2,203,337 Mebold June 4, 1940 2,511,524Adler June 14, 1950 2,615,948 Kamen Oct. 28, 1952 2,677,108 Brady Apr.27, 1954 FOREIGN PATENTS 455,196 Great Britain Oct. 15, 1936

